He played college football for the Florida State Seminoles and was selected by the Detroit Lions in the first round of the 2006 NFL draft.
[5] At Florida State, Sims wore #34, a number that was retired in honor of former Seminole football player, Ron Sellers.
[6] In 2003, as a true freshman at Florida State, Sims played in all 13 games of the season, including the Orange Bowl against Miami (FL), as a back-up outside linebacker.
In July 2005, Sims was arrested on charges of battery and resisting an officer, allegedly shoving his then-girlfriend "repeatedly to the ground" during an argument in the parking lot of a FSU residence hall.
Described as a "three-down linebacker who plays bigger than his listed size", Sims was selected as ninth overall in the first round of the 2006 NFL draft by the Detroit Lions.
On December 31, Sims made a key tackle on fourth down to give the Lions a big win against the Dallas Cowboys.
The Lions former head coach, Rod Marinelli, said that Sims' resembled that of Tampa Bay Buccaneers linebacker Derrick Brooks in his early years, being described as a fast, punishing, sure-tackler.
After the loss of Sean Lee to injury, on October 24, 2012, the Dallas Cowboys signed him as an unrestricted free agent to provide depth at linebacker.
Sims quickly became a starter by his second game (against the Atlanta Falcons) and eventually the unit's defensive play caller, after injuries decimated the position further.
[14] He also recorded 10 tackles in the Cowboys' emotional week 14 win against the Cincinnati Bengals, a day after the team received news of the death of Jerry Brown and the arrest of Josh Brent.
[15] He registered 42 tackles, a forced fumble and started 6 games while replacing Bruce Carter, Justin Durant and Sean Lee at different times.
[17] [18] Key On May 29, 2009, Sims married Brooke McGriff, who is pursuing a degree in education at Tallahassee Community College.